Junos OS: If in a scaled CoS scenario information on CoS state is gathered mgd processes get stuck

Summary

An Improper Handling of Exceptional Conditions vulnerability in the Class of Service daemon (cosd) of Juniper Networks Junos OS allows an authenticated, network-based attacker with low privileges to cause a limited Denial of Service (DoS). In a scaled CoS scenario with 1000s of interfaces, when specific low privileged commands, received over NETCONF, SSH or telnet, are handled by cosd on behalf of mgd, the respective child management daemon (mgd) processes will get stuck. In case of (Netconf over) SSH this leads to stuck SSH sessions, so that when the connection-limit for SSH is reached, new sessions can't be established anymore. A similar behavior will be seen for telnet etc. Stuck mgd processes can be monitored by executing the following command:   user@host> show system processes extensive | match mgd | match sbwait This issue affects Juniper Networks Junos OS: • All versions earlier than 20.4R3-S9; • 21.2 versions earlier than 21.2R3-S7; • 21.3 versions earlier than 21.3R3-S5; • 21.4 versions earlier than 21.4R3-S5; • 22.1 versions earlier than 22.1R3-S4; • 22.2 versions earlier than 22.2R3-S3; • 22.3 versions earlier than 22.3R3-S2; • 22.4 versions earlier than 22.4R3; • 23.2 versions earlier than 23.2R1-S2, 23.2R2.

Timeline

1. Apr 12, 2024, 2:55 PM UTCCVE published
2. Jul 31, 2024, 5:38 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. May 19, 2025, 9:22 AM UTCRecord last updated

Affected versions

• Juniper Networks Junos OS

  fixed in 20.4R3-S9; From 21.2 · fixed in 21.2R3-S7; From 21.3 · fixed in 21.3R3-S5; From 21.4 · fixed in 21.4R3-S5; From 22.1 · fixed in 22.1R3-S4; From 22.2 · fixed in 22.2R3-S3; From 22.3 · fixed in 22.3R3-S2; From 22.4 · fixed in 22.4R3

References 1